1. Field of the Invention
The invention relates generally to pumping systems employing pumping cartridges that can be disengaged from a pump drive unit, and, more specifically to methods of joining a pumping cartridge to a pump drive in such pumping systems and interconnect mechanisms facilitating such methods.
2. Description of the Related Art
A piston pump typically includes several cooperating elements. These typically include at least a cylinder, a piston moving in the cylinder, and a drive shaft connected to the piston that moves the piston back and forth in the cylinder. Other elements typically include one or more check valves, or functional equivalents, so that fluid is drawn in from a source and expelled into an outlet. Normally, the drive shaft is permanently fastened to a mechanism providing the reciprocal motion.
In certain medical applications, it may be desirable to provide disposable pump elements that contact fluids being pumped, e.g. disposable piston pumping cartridges, for example to prevent transmission of disease between patients. For the sake of economy, it may be advantageous for the mechanism providing reciprocating force to be separate from the pumping elements. The disposable portion of a piston pump, typically comprising a cylinder, a piston, and valves, can advantageously be fabricated as a separate cartridge. The cartridge can, for certain applications, be provided in a sterile condition, so that the fluid pumped will not be contaminated. Such a cartridge can be configured to be reversibly attached to a reusable drive mechanism, typically comprising a motor, which reciprocates the piston via, for example, a reversible linkage.
In one mode of medical use, such as described in certain of the Applicant's commonly owned patents and patent applications (e.g. U.S. Pat. Nos. 6,216,573; 5,944,686; 6,375,635; 6,511,493; and U.S. Pat. Application Pub. No. 2002/0176788-A1, each incorporated herein by reference), such a disposable cartridge can used to generate a high pressure, such as 5,000 p.s.i, 10,000 p.s.i, or 20,000 p.s.i or more. The resulting high pressure water jet can be used, for example, to cut and/or remove and/or clean tissue, or to drive rotary tissue-abrading elements. In one mode of making such cartridges, described in more detail in commonly-owned US 2002/0176788-A1, the piston is provided with an abradable flange as a sealing element. Such disposable cartridges may, in certain embodiments, be designed to be used only for a single medical procedure, and thus may require relatively frequent replacement.
In a medical environment, such as an operating room, there are several constraints that may be desirable to be satisfied in a procedure for coupling a piston to a drive that make such a procedure technically challenging. First, it may be desirable that the connection can be made without removing the piston from the cylinder, since that would tend to render the pumping zone non-sterile. Second, may be desirable for it to be possible for the operator to be able to replace the pump while the operator is wearing gloves, and without contaminating the operator (who will typically be a physician or a nurse.) Third, it may be desirable that the connection method can enable the disposable components to be coupled to the reusable components reliably on the first try and without extensive operator training or difficulty. In addition, it may be desirable that the connection mechanism be able to be fabricated economically so as to add as little expense to the overall disposable cartridge as possible.